Improve search responsiveness
When user is redirected to search page from other page and searchindex is not cached and is big (800k or more), the search may appear broken to user. This is described in http://bugs.python.org/issue7731
The patch below make search page load index only after form controls are animated and user is receiving feedback of what is going on. The proper version would, of course, display message "Caching search index 20k/800k 2.5% complete..." and used received JSON directly instead of reevaluating it, but this requires more time to develop that I had to research this problem.